Shunt trip and undervoltage device

ABSTRACT

Undervoltage and shunt trip units for a multi-phase molded case circuit breaker are each constructed with a primary latch operated by the armature of an electromagnet. The primary latch acts through a secondary latch to hold an intermediate member in latched position, wherein the latter holds an actuator in its inactive position. When the latches are released to release the intermediate member, a coiled tension spring acting directly upon the actuator moves the latter to a tripping position to trip the contact latching mechanism of the circuit breaker. Another spring, separate from the actuator operating spring, biases the magnet armature away from the magnet yoke so that adjustment of the armature spring will not alter the force with which the actuator is moved to its tripping position.

United States Patent 1 Shaffer et al.

[54] SHUNT TRIP AND UNDERVOLTAGE DEVICE [75] Inventors: Howard R.Shaffer, Glenside, Pa.;

Albert Strobel, Cherry Hill, NJ.

[58] Field of Search ..335/20, 7, 169, 170, 174, 21

[56] References Cited I UNITED, STATES PATENTS 6/1967 Shaffer.....335/20 3,175,064 3/1965 Myers..... 1,292,651 l/19l9 Rippl ..335/7[4 1 Mar. 27, 1973 FOREIGN PATENTS OR APPLICATIONS PrimaryExaminerl-lar0ld Broome Attorney-Ostrolenk, Faber, Gerb & Soffen [57]ABSTRACT Undervoltage and shunt trip units for a multi-phase molded casecircuit breaker are each constructed with a primary latch operated bythe armature of an electromagnet. The primary latch acts through asecondary latch to hold an intermediate member in latched position,wherein the latter holds an actuator in its inactive position. When thelatches are released to release the intermediate member, a coiledtension spring acting directly upon the actuator moves the latter to atripping position to trip the contact latching mechanism of the circuitbreaker. Another spring, separate from the actuator operating spring,biases the magnetarmature away from the magnet yoke so that adjustmentof the armature spring will not alter the force with which the actuatoris moved to its tripping 7 position.

9 Claims, 11 Drawing Figures Great Britain .335/169 v Patented March 27,1973 3,723,924

4 Sheets-Sheet 1 Patented March 27, 1973 4 Sheets-Sheet 2 ATTORNEYSPatented Match 27, 1973 4 Sheets-Sheet 5 ATTORNEYS Patented March27,'1973 4 Shoets-Sheet 4 M EUR m b E SHUNT TRIP AND UNDERVOLTAGE DEVICEThis invention relates to molded case circuit breakers in general, andmore particularly relates to constructions for auxiliary undervoltageand shunt trip units.

Shunt trip and undervoltage auxiliary units for tripping the contactholding latch of multi-phase molded case circuit breakers are disclosedin U. S. Pat. No. 3,175,064 issued Mar. 23, 1965 to F. E. Myers forf-Shunt Trip and Undervoltage Device" and U.S. Pat. No. 3,324,428 issuedJune 6, 1967 to H. R. Shaffer for Shockproof Shunt Trip Unit forTripping Open the Contacts of a Circuit Breaker. Auxiliary trippingunits of these types are used for the opening of a circuit breakerindependently of the magnitude of load current. The undervoltage deviceautomatically operates to trip the circuit breaker when line voltagefalls below a predetermined safe level and the shunt trip device is usedto open the circuit breaker from a location remote thereto.

A primary object of this invention is to provide shunt trip andundervoltage devices that incorporate most of the desirable features ofsimilar prior art devices in a novel and improved structure. Inparticular, as will hereinafter be seen, auxiliary tripping units,constructed in accordance with teachings of the instant inventioninclude the following desirable features.

1 Adjustment of the auxiliary unit is not required after mounting in acircuit breaker.

2. The auxiliary unit is readily mounted in a circuit breaker by twoscrews that are readily accessible for tightening at the front of thecircuit breaker.

3. Undervoltage and shunt trip units are interchangeable without thenecessity of adjusting any parts of the circuit breaker. I

4. The units are relatively compact.

5. The actuator for the auxiliary unit is constructed and mounted forlarge overtravel.

6. Adjustment of the magnet armature opening spring force is independentof the spring force which moves the actuator to its tripping position.

7. The spring which operates the actuator to its tripping position actsdirectly on the latter rather than through intermediate members, therebysubstantially reducing sliding and other friction forces present inprior art devices having one or more members interposed between theactuator and its operating spring.

8. The pivots for all levers are on a common frame element to facilitatethe holding of close tolerances between pivot centers.

9. The units are shock-proof without the addition of counterweights inthat their respective armatures are balanced and pivoted at theircenters.

The foregoing object and features as well as additional objects andfeatures of the instant invention will become readily apparent afterreading the following description of the accompanying drawings in which:

FIG. I is a plan view of a circuit breaker with a portion of its covercut away to reveal an auxiliary trip unit constructed in accordance withteachings of the instant invention.

FIGS. 2 and 3 are side elevations of a shunt trip unit constructed inaccordance with teachings of the instant invention. In FIG. 2 the unitis in its latched position, and in FIG. 3 the unit is tripped.

FIG. 4 is a side elevation of the primary latch member for the shunttrip unit of FIGS. 2 and 3.

FIGS. 4A and 4B are a plan view and a front elevation, respectively, ofthe primary latch member of FIG. 4, looking in the directions of therespective arrows 4A4A and 4B-4B.

FIG. 5 is a side elevation of an undervoltage unit constructed inaccordance with teachings of the instant invention, with the unit beingin its latched position.

FIG. 6 is a front elevation of the unit of FIG. 5, looking in thedirection of arrows 6-6 of FIG. 5.

FIG. 7 is a side elevation of the primary latch member of FIG. 5.

FIGS. 7A and 7B are a plan view and a front elevation, respectively, ofthe primary latch member of FIG. 7, looking in the direction of therespective arrows 7A7A and 7B7B of FIG. 7.

Now referring to the figures. Multi-phase molded case circuit breaker 10of FIG. 1 is provided with auxiliary shunt trip unit (FIGS. 2 and 3),secured by two machine screws 16 to the forward surface 17 of metalbracket 18 mounted to wall 19 of plastic housing 21 for replaceable tripunit 20. Shunt trip unit 15 includes an electromagnet consisting ofgenerally U-shaped yoke 23 having one leg thereof extending throughenergizing coil 25 and movable armature 24 pivotally mounted at itsmid-point to pin 26. Cable 27, having connector 28 at one end thereof,is connected at its other end to magnet coil 25. Cable 27 passes throughwasher-like strain relief member 98 mounted to the rear end ofinsulating arm 29 whose forward end is secured by rivets 31 to leg 32 offrame member 33.

Screw 34 extends through clearance aperture 36 in primary latch member35 and secures the latter to the forward surface of armature 24.Clearance hole 37 in rearwardly extending leg 38 of member 35 providesclearance for pivot pin 26. One end of coiled tension spring 39 ishooked into aperture 41 in forwardly extending arm 42 of primary latchmember 35. The other end of spring 39 is connected to one end ofadjusting screw 43 which extends through a clearance aperture in ear 44of frame member 33 and is threadably engaged by adjusting nut 45. Thus,it is seen that spring 39 biases armature 24 in a clockwise directionabout pivot pin 26, thereby tending to form an air gap between armature24 and pole face 46 of yoke 23, as shown in FIG. 2.

With armature 24 spaced from pole face 46, latching tip 47 of primarylatch 35 engages the left lower portion 51a of secondary latch 48. Thelatter is pivotally mounted at pin 49 to frame member 33. In turn, theright lower extension 51 of secondary latch 48 engages hooked portion 52of intermediate member 50, thereby maintaining the latter in its latchedposition shown in FIG. 2.

Intermediate member 50 is pivoted at pin 53 mounted to frame member 33.Cam surface 54 at the end of intermediate member 50 remote from hook 52is in engagement with surface 55 of actuator 56. The latter is pivotallymounted to pin 57, also secured to frame member 33 in parallel relationto pivot pins 26, 49 and 53. Coiled tension spring 58 is secured at oneend thereof directly to the rear of actuator 56 and the other end ofactuator spring 58 is secured to pivot pin 53.

Bar 59 at the forward end of actuator 56 engages adjustable lengthextension 61, threadably mounted near the freeend of tripper barextension 62. Lock-nut 63 maintains extension 61 in its adjustedposition. When actuator 56 is released and is moved counterclockwise byspring 58, actuator ear 59 moves to the left with respect to FIG. 2 toengage extension 61, thereby pivoting common tripper bar 64 in acounterclockwise direction to release the contact holding latch means(not shown) for the overcenter spring mechanism (not shown) whichoperates movable contact arm 65 to bring movable contact 66 into and outof engagement with stationary contact 67.

With shunt trip unit in its latched position of FIG. 2 and contacts 66,67 in engagement, the free end of spring element 68 extending fromintermediate member 50 is spaced from contact arm 65. Energization ofoperating coil 25 causes armature 24 and primary latch member 35 mountedthereto to pivot in a counterclockwise direction with latch tip 47moving forward of lower left extension 51a of secondary latch 48. The

sion 68 to pivot intermediate member 50 in a counter-- clockwisedirection so that cam surface 54 acts on actuator surface 55 to pivotactuator 56 in a clockwise direction to its inactive position of FIG. 2.In addition,

after intermediate member hook 52 moves forward of secondary latchextension 51, intermediate member surface 69 engages secondary latch 48and pivots the latter in a counterclockwise direction, so that extension51a thereof moves clear of primary latch tip 47 and permits armature 44to move to its fully open position of FIG. 2. Thereafter, as contact arm65 moves to maintain intermediate member 50a in the latched position ofFIG. 5 wherein cam surface 54 thereof maintains actuator 56 in itsinactive position, shown in FIG. 5. With the circuit breaker contactsclosed, when the voltage energizing coil a falls below a predeterminedvalue, the flux generated by current flowing in coil 25a is insufficientto exert a holding force in excess of the opening force generated byspring 39.

Thus, the latter rotates armature 24 and primary latch member 35acarried thereby in a clockwise direction, so that primary latching tip47a moves below secondary latch extension 51b and secondary latch 48counterclockwise direction to operate common trip bar latch 48counterclockwise until lower leftextension 51b thereof is clear ofprimary latching tip 47a. Thereafter, resetting hump 50b moves armature24 into engagement with pole face 46. In this position of armasothat themagnet coil 25a energized sufficiently to hold armature 24 against poleface 46, as contact arm closed circuit position, the elements of shunttrip unit 15 assume the operative latching positions shown in FIG. 2.

Now referring more particularly to FIGS. 5-7B. Except for the four areasnoted below, undervoltage trip unit 75 is of the same constructionasshunt trip unit 15.

That is, shunt trip unit 15'does not have shading coil 74 ofundervoltagetrip unit 75; latch tip 47a of undervoltage unit primary latch member350 is different than shunt trip unit primary latch member 35;undervoltage trip unit holding coil 25a is rated for continuous duty,whereas shunt trip unit operating coil 25 is rated for intermittentduty; and shunt trip unit intermediate member 50 is not provided withhump 50b found in undervoltage unit intermediate member 50a. Hump 50bengages the rear surface of armature 24' as intermediate moves to closedcircuit position the elements of undervoltage trip unit move to theirrespective positions'shown in FIG. 5.

It is noted that even though extension 61 of tripper bar extension 62 isillustrated as being adjustable, in practice, because of the relativelylarge travel of actuator ear 59, extension 61 need not be adjustablymounted to tripper bar 64.

Although there have been described preferred embodiments of this novelinvention, many variations and modifications will now be apparent tothose skilled in the art. Therefore, this invention is to be limited notby the specific disclosure herein but only by the, appending claims.

The embodiments of the invention in which an exclusive privilege orproperty is claimed are defined as follows.

i 1. An auxiliary unit for tripping the contacts of a circuit breaker toopen position and acting independently of circuit breaker load current;said auxiliary unit including an electromagnet having a core and anarmature biased toward a first position away from said core and movableto a secondposition closer to said core than said first position, alatch means operable by said armature, an intermediate member held in alatched position by engagement with said latch means, an actuator heldin an inactive position by said intermediate member, and biasing meansfor operating said actuator to a tripping position to trip a circuitbreaker contact latching mechanism when-the actuator is no longerrestrained by said intermediate member; said actuator being positionedat one end of said intermediate member and said latch means beingpositioned at the there is a spring, independent of said biasing meansother end thereof; said intermediate member being mounted intermediateits ends to a first pivot; said first pivot being closer to said one endthan to said other end; a second pivot to which said armature ismounted; said latch means including a primary latch connected to saidarmature for movement thereby and a secondary latch held in latchingposition by engagement with said primary latch; said intermediate memberheld in said latched position by engagement with said secondary latch; athird pivot to which said secondary latch is mounted; a fourth pivot towhich said actuator is mounted; and a common member to which all of saidpivots are mounted.

2. An auxiliary unit as set forth in claim 1 in which the second pivotextends generally through the center of the armature.

3. An auxiliary unit as set forth in claim 1 in which biasing saidarmature to its said first position; and means for adjusting the loadingof said spring.

4. An auxiliary unit as set forth in claim 3 in which said biasing meanscomprises a tension spring connected at one end to said actuator and atthe other end to said first pivot.

5. An auxiliary unit as set forth in claim 1 in which the primary andsecondary latches are reset by forces applied thereto through saidintermediate member.

6. An auxiliary device as set forth in claim 1 in which the intermediatemember is maintained in latched position when said armature is in saidfirst position.

7. An auxiliary device as set forth in claim 1 in which the intermediatemember is maintained in latched position when said armature is in saidsecond position.

8. An auxiliary unit as set forth in claim 1 in which there is a springextension for said intermediate member through which a relatching forceis applied to said unit; said spring extension being connected to saidintermediate member at a point located between said first pivot and saidother end of said intermediate member.

9. An auxiliary unit as set forth in claim 8, said one end of saidintermediate member engages said actuator; and a cam means at the areaof engagement between said one end and said intermediate member.

1. An auxiliary unit for tripping the contacts of a circuit breaker toopen position and acting independently of circuit breaker load current;said auxiliary unit including an electromagnet having a core and anarmature biased toward a first position away from said core and movableto a second position closer to said core than said first position, alatch means operable by said armature, an intermediate member held in alatched position by engagement with said latch means, an actuator heldin an inactive position by said intermediate member, and biasing meansfor operating said actuator to a tripping position to trip a circuitbreaker contact latching mechanism when the actuator is no longerrestrained by said intermediate member; said actuator being positionedat one end of said intermediate member and said latch means beingpositioned at the other end thereof; said intermediate member beingmounted intermediate its ends to a first pivot; said first pivot beingcloser to said one end than to said other end; a second pivot to whichsaid armature is mounted; said latch means including a primary latchconnected to said armature for movement thereby and a secondary latchheld in latching position by engagement with said primary latch; saidintermediate member held in said latched position by engagement withsaid secondary latch; a third pivot to which said secondary latch ismounted; a fourth pivot to which said actuator is mounted; and a commonmember to which all of said pivots are mounted.
 2. An auxiliary unit asset forth in claim 1 in which the second pivot extends generally throughthe center of the armature.
 3. An auxiliary unit as set forth in claim 1in which there is a spring, independent of said biasing means, biasingsaid armature to its said first position; and means for adjusting theloading of said spring.
 4. An auxiliary unit as set forth in claim 3 inwhich said biasing means comprises a tension spring connected at one endto said actuator and at the other end to said first pivot.
 5. Anauxiliary unit as set foRth in claim 1 in which the primary andsecondary latches are reset by forces applied thereto through saidintermediate member.
 6. An auxiliary device as set forth in claim 1 inwhich the intermediate member is maintained in latched position whensaid armature is in said first position.
 7. An auxiliary device as setforth in claim 1 in which the intermediate member is maintained inlatched position when said armature is in said second position.
 8. Anauxiliary unit as set forth in claim 1 in which there is a springextension for said intermediate member through which a relatching forceis applied to said unit; said spring extension being connected to saidintermediate member at a point located between said first pivot and saidother end of said intermediate member.
 9. An auxiliary unit as set forthin claim 8, said one end of said intermediate member engages saidactuator; and a cam means at the area of engagement between said one endand said intermediate member.